The present invention concerns cloned human neurokinin-1 receptor (human NK1R) and recombinant human NK1R. Neurokinin-1 receptor is also known as substance P receptor.
J. Yokota, et al., J. Biol. Chem., 264:17649 (1989) have reported cloned rat neurokinin-1 receptor. N. P. Gerard, et al., J. Biol. Chem., 265:20455 (1990), have reported human neurokinin-2 receptor. Cloned rat and bovine neurokinin-2 receptor have likewise been reported. See respectively, Y. Sasi, and S. Nakanishi, Blochem Biophys. Res. Comm., 165:695 (1989), and Y. Masu, et al., Nature 329:836 (1987). Cloned rat neurokinin-3 receptor has also been reported by R. Shigemoto, et al., J. Biol. Chem., 265:623 (1990).
The above references, however, neither disclose or suggest the instant invention. In particular, the pharmacological profile of the human receptor differs significantly from the rat. Moreover, the rat neurokinin-1 receptor differs from the NK1R disclosed herein by 23 amino acids.
Substance P is a naturally occuring undecapeptide belonging to the tachykinin family of peptides. Substance P is a pharmacologically-active neuropeptide that is produced in mammals. Its characteristic amino acid sequence is illustrated in U.S. Pat. No. 4,680,283. As is well known in the art substance P and other tachykinins have been implicated in the pathophysiology of numerous diseases. Substance P has been shown to be involved in the transmission of pain or migraine (see B. E. B. Sandberg et al., Journal of Medicinal Chemistry, Vol. 25, p. 1009 (1982)), as well as in central nervous system disorders such as anxiety and schizophrenia, in respiratory and inflammatory diseases such as asthma and rheumatoid arthritis, respectively, and in gastrointestinal disorders and diseases of the GI tract, like ulcerative colitis and Crohn's disease, etc. (see D. Regoli in "Trends in Cluster Headache," edited by F. Sicuteri et al., Elsevier Scientific Publishers, Amsterdam, 1987, pp. 85-95).
The instant invention also concerns an assay protocol which can be used to determine substance P activity in body fluids. The assay can also be used for identifying and evaluating substances that bind substance P receptor. Thus, the assay can be used to identify substance P antagonists and evaluate their binding affinity. Other methods includes that described by M. A. Cascieri, et al., J. Biol. Chem., 258-5158 (1983). By use of such methods, substance P antagonists have been identified. See, for example, R. M. Snider, et al., Science, 251:435 (Jan. 1991) and S. McLean, et al., Science, 251:437 (Jan. 1991). See also WO90/05525 which published May 31, 1990, which is hereby incorporated by reference. Methods to date have proven inferior, in part, for failure of the animal receptor (animal NK1R, NK2R or NK3R) activity to accurately reflect that of human neurokinin-1 receptor. Furthermore, prior to this disclosure human NK1R has not been available in a purified form or in substantial isolation from NK2R and/or NK3R. Use of such neurokinin receptor sources can not accurately depict the affinity for human NK1R.